JP2005089275A - Method for producing glass formed body, method for producing glass material for press molding and method for producing optical element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing an optically homogeneous rod glass formed body or a plate glass formed body from a molten glass while holding a space for a subsequent step easily, a method for producing a glass material for press molding from the glass formed body and a method for producing an optical element to press-mold the glass material for press molding. <P>SOLUTION: The glass formed body is formed by molding the molten glass into a solid rod glass or plate glass while it is poured into a through-hole of a mold having the through-hole. The method for producing the glass material for the press molding comprises a step to cut the produced glass formed body to cross its central axis. The method for producing the optical element comprises obtaining a press-molded product by the press molding of the produced glass material after heating and softening. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for forming solid rod-like glass and plate-like glass from molten glass, a method for producing a glass material for press molding using the method, and a press by heating and softening the material for press molding. The present invention relates to a method for manufacturing an optical element to be molded.

  As a method of forming rod-shaped or plate-shaped glass, a method is known in which molten glass is continuously cast into a mold and the molded glass is drawn out from one opening. For example, in Japanese Patent Application Laid-Open No. 52-6719 (Patent Document 1) and Japanese Patent Application Laid-Open No. 52-6720 (Patent Document 2), a mold is arranged so that a flow path of cast glass is horizontal. A method is disclosed in which molten glass is poured into the glass, glass formed from one opening is drawn out, and optical glass is continuously formed.

  However, according to the study by the present inventors, when a rod-like or plate-like glass is formed by the method disclosed in Patent Documents 1 and 2, inhomogeneity occurs in the glass, resulting in defects called striae. Turned out to be. In the methods disclosed in Patent Documents 1 and 2, the molten glass is poured from a molten glass outlet pipe disposed above at a substantially right angle with respect to a horizontally disposed mold. Therefore, the cast glass is formed into a glass rod or a glass plate after being bent at a substantially right angle in the mold. At the corner of the mold where the molten glass stream is bent at a right angle, the molten glass flowing outside the corner takes a longer path than the molten glass flowing inside the corner. Therefore, in the glass rod obtained by this method, the glasses that have passed through different paths in the mold are located on the same vertical section with respect to the flow direction. In this way, it is considered that the glasses that have passed through different paths in the process of being cooled and molded in the mold are located on the same cross section, which causes inhomogeneities in the glass. In general glass, such inhomogeneity is not a problem, but in optical glass, such inhomogeneity becomes a defect called striae. The above problem is particularly remarkable when the viscosity of the molten glass to be cast is low or when the ratio of the width to the thickness (width / thickness) is large when forming the sheet glass.

On the other hand, Japanese Patent Application Laid-Open No. 60-251136 (Patent Document 3) discloses a method of forming a rod-shaped glass by pulling a molten glass cast into a pipe-shaped mold vertically or at an angle of 45 °. Yes. However, in the method of forming the rod-shaped glass by drawing the molten glass vertically, it is difficult to secure a space for subsequent processes such as annealing after forming. Therefore, the method described in Patent Document 3 is not appropriate as a method for continuously mass-producing glass. Moreover, in patent document 3, although the glass viscosity has shape | molded the molten glass about 10 < ² > -10 < ³ > Pa * s, the glass currently used recently has a lower viscosity of a molten glass, and the said method is favorable. It was not possible to form a rod-like glass.
JP 52-6719 A JP 52-6720 A JP 60-251136 A

  The present invention has been made to solve the above-mentioned problems, and manufactures an optically homogeneous rod-shaped glass sheet or sheet-shaped glass molded body from molten glass while easily securing a space for subsequent processes such as annealing. And a method for producing a glass material for press molding for use in press molding from the glass molded body, and an optical element for press molding using the glass material for press molding An object is to provide a manufacturing method.

Means for achieving the above object are as follows.
[Claim 1] In a method for producing a glass molded body, in which molten glass is formed into a solid rod-like glass while being poured into a through-hole of a mold having a through-hole,
In the through hole, two openings are connected linearly,
The mold is arranged so that the central axis of the through hole is inclined,
A molten glass having a viscosity of ¹ dPa · S or more and less than 10 ² dPa · S is continuously poured from the opening on the high position side of the through hole, and the rod-shaped glass is continuously poured from the opening on the low position side of the through hole. A method for producing a glass molded body, characterized in that the molten glass is drawn out and the molten glass is poured while maintaining a molten glass liquid level at an opening on the high position side at a predetermined height.
[Claim 2] In a method for producing a glass molded body, in which molten glass is molded into a sheet glass while being poured into a through-hole of a mold having a through-hole,
In the through hole, two openings are connected linearly,
The mold is arranged so that the central axis of the through hole is inclined,
The molten glass is continuously poured from the opening on the high position side of the through hole, the plate glass is continuously drawn from the opening on the low position side of the through hole, and the molten glass is poured, A method for producing a glass molded body, wherein the molten glass liquid level in the opening on the high position side is maintained at a predetermined height.
[3] The method for producing a glass molded body according to [1] or [2], wherein the temperature of the mold is controlled so that the surface temperature of the glass drawn from the through hole is equal to or lower than the glass yield point.
[Claim 4] When the transport path of the glass drawn from the through hole is changed before annealing, the glass is heated so that the surface temperature of the glass becomes equal to or higher than the glass yield point before the transport path is changed. 4. The method for producing a glass molded body according to any one of 3 above.
[5] A method for producing a glass material for press molding, comprising a step of cutting the glass molded body produced by the method according to any one of [1] to [4] so as to cross its central axis.
6. The method for producing a glass material for press molding according to claim 5, further comprising a step of machining the cut glass to produce a glass material for press molding.
[7] A method for producing an optical element, comprising heating and softening a press-molding glass material produced by the method according to [5] or [6] and then press-molding to obtain a press-molded product.
[8] The method for producing an optical element according to [7], further comprising grinding and / or polishing the press-formed product.

  According to the present invention, an optically homogeneous solid rod-shaped glass molded body and plate-shaped glass molded body can be produced from molten glass. According to the present invention, it is easy to secure a space for subsequent processes such as annealing, and glass can be continuously mass-produced. Moreover, a homogeneous glass material for press molding for use in press molding can be produced from the glass molded body, and there is no defect such as striae by press molding using the glass material for press molding. A good optical element can be manufactured with high productivity.

  The first aspect of the present invention relates to a method for producing a glass molded body for forming a solid rod-like glass (hereinafter also simply referred to as “rod-shaped glass”) from molten glass, and the second aspect of the present invention relates to a molten glass. The present invention relates to a method for producing a glass molded body for molding a sheet glass. In this specification, “rod glass” has a cross-sectional shape such as a circle, an ellipse, a square, a rectangle having a long side length to long side length ratio (long side length / short side length) of 2 or less, and a polygon. A glass molded body. In the present invention, “plate glass” refers to a glass plate having a ratio of width to thickness (width / thickness) of more than 2.

(First aspect)
The 1st aspect of this invention is related with the manufacturing method of the glass forming body which shape | molds molten glass into a rod-shaped glass, pouring into the casting_mold | template which has a through-hole. In the manufacturing method according to the first aspect, the through hole has two openings linearly connected to each other, and the mold is arranged so that a central axis of the through hole is inclined, and the through hole is formed. A molten glass having a viscosity of ¹ dPa · S or more and less than 10 ² dPa · S is continuously poured from the opening on the high position side of the hole, and the rod-shaped glass is continuously drawn out from the opening on the low position side of the through hole, The molten glass is poured while maintaining the molten glass liquid level at the opening on the high position side at a predetermined height to produce a glass molded body. The first aspect will be described below with reference to the drawings.

  FIG. 1 shows an example of the first aspect of the present invention, and is a schematic view of a state in which molten glass is cast and formed into a rod-like glass from the side. The mold part is shown in a vertical section so that the inside can be seen.

  First, the mold 11 is arranged so that the central axis of the through hole is inclined. Here, if the angle between the central axis of the through hole and the horizontal plane is θ, θ is preferably in the range of 30 to 60 °. In FIG. 1, θ is 45 °. In order to make the path length in the through hole of the molten glass constant regardless of the distance from the central axis, it is preferable that θ is large. However, if θ is increased, it is pulled out from the through hole as described later. If the glass transport path is changed before annealing, the glass must be bent greatly. On the other hand, if θ is too small, the path length in the through hole of the molten glass varies depending on the location, causing striae. It becomes easy. From the above viewpoint, θ is preferably in the range of 30 to 60 °, and more preferably in the range of 40 to 50 °. However, depending on the type of glass, there is a glass that is difficult to cause striae, and in the case of using such a glass, θ can be set to a range of 5 to 10 °, for example. The angle θ is preferably determined in consideration of the viscosity of the molten glass flowing out, the shape and dimensions of the target glass molded body, and the like.

  Next, in a state where the central axis of the through hole of the mold is inclined, molten glass is continuously poured from an opening portion (hereinafter referred to as “casting port”) 13 at a high position among the opening portions at both ends of the through hole. Here, it is preferable to arrange the mold 11 so that the casting port 13 is located directly below the outflow pipe 12 that flows down the molten glass, and pour the molten glass into the center of the liquid glass level surface in the through hole. By doing in this way, the length of the movement path | route of the glass within a casting_mold | template can be arrange | equalized uniformly, and striae can be prevented effectively.

  A molten glass tank (not shown) in which molten glass that has been melted, clarified, and homogenized is accumulated is disposed on the upper portion of the outflow pipe 12, and from there, the molten glass is preferably passed through the outflow pipe 12. It is made to flow down continuously at a flow rate of. The molten glass that has flowed down is poured into the through-hole from the casting port of the mold, and, as shown in FIG. 1, the predetermined glass in the through-hole is continuously flown out from the outflow pipe 12 without interruption. Fills molten glass to height.

In the first aspect, the viscosity of the molten glass flowing out from the outflow pipe is ¹ dPa · S or more and less than 10 ² dPa · S. According to the manufacturing method of the first aspect, an excellent striae prevention effect can be obtained in the molding of a molten glass having a viscosity in the above range. The viscosity is preferably in the range of ² dPa · S or more and less than 10 ² dPa · S, and more preferably in the range of ^{2 to} 90 dPa · S. By setting it as the said viscosity range, shaping | molding can be performed easily.

  The molten glass poured into the through hole comes into contact with the inner wall of the through hole and cools while moving obliquely downward along the central axis direction of the through hole. Glass whose heat has been removed by the mold and increased in viscosity is drawn out from an opening (hereinafter referred to as “drawer port”) 14 at a low position of the mold through hole, and is formed into a rod-shaped glass (hereinafter also referred to as “glass rod”). Can be molded. It is desirable to adjust the viscosity, the inflow amount, and the drawing speed of the molten glass until the glass rod is pulled out from the drawing port 14, and move the molten glass in the through hole in a state where it is in contact with the inner wall of the through hole without any gap. By shaping so that there is no gap between the inner wall of the through hole and the molten glass, the area where the glass in the high temperature state is exposed to the outside air can be minimized. Thereby, since the volatilization of the volatile component in the glass can be reduced, it is possible to prevent deterioration of the portion in contact with the outside air, and it is also possible to prevent striae caused by volatilization.

  In the mold used in the present invention, the two openings are linearly connected. Since the two openings are in linear communication, there is no significant difference between the length of the movement path of the glass flowing along the central axis of the through hole and the length of the movement path of the glass flowing along the inner wall of the through hole. . Therefore, unlike the molding method in which the molten glass is bent vertically in the mold, the occurrence of striae can be effectively prevented.

  Furthermore, in the present invention, it is desirable to keep both the speed at which the molten glass flows out from the outflow pipe (that is, the speed at which the molten glass flows into the mold) and the speed at which the glass rod is drawn out from the outlet. Moreover, it is preferable to control the liquid amount of the molten glass poured into the mold and the drawing speed of the glass rod so that the molten glass liquid surface is maintained at a predetermined height in the through hole. If the drawing speed of the glass rod from the mold is high or the inflow speed of the molten glass is too low, a gap is formed between the inner wall of the through hole and the glass rod, and the outer diameter of the glass rod is not stable. On the other hand, when the drawing speed is slow or the inflow speed is too high, the molten glass overflows from the mold or the shape of the glass rod becomes defective. If the amount of the molten glass poured into the mold and the drawing speed of the glass rod are controlled so that the molten glass liquid surface is maintained at a predetermined height in the through hole, between the inner wall of the through hole and the molten glass, Or it can shape | mold so that there may be no clearance gap between glass rods. As a result, the area where the glass in the high temperature state is exposed to the outside air can be minimized, and volatilization of the volatile components in the glass can be reduced. The striae caused by can also be prevented.

  The temperature of the mold is determined in consideration of the following points: (1) the glass does not melt, (2) no glass breakage called canister, (3) the molten glass spreads in the mold through-holes without any gaps. It is preferable to do. The mold may be provided with a heater or a cooler as necessary for temperature control. Moreover, it is preferable that the temperature of the glass rod surface in a drawer port is the temperature below a glass yield point. If the temperature of the surface of the glass rod at the outlet is a temperature below the glass yield point, the glass rod can be prevented from being deformed when being drawn out from the mold. In addition, since glass can be deformed by an external force at a temperature equal to or higher than the yield point, as will be described later, when bending a glass rod pulled out from the drawer port in a direction that facilitates subsequent processes, the drawer port It is preferable that the temperature of the glass rod surface in is a temperature above the yield point. If the temperature of the glass rod surface at the outlet is too high, the mold is cooled by air cooling or by providing a water cooling plate, and if the temperature is too low, it is heated by a heater. By doing so, it can be adjusted.

  The mold temperature can be 20-50 ° C. lower than the glass transition temperature near the casting port, and 0-30 ° C. lower than the glass transition temperature near the drawer port. In the intermediate portion, the temperature is not more than the temperature near the casting port and can be not less than the temperature near the drawer port.

  From the viewpoint of preventing glass fusion, cracking, spreading, bending, and the like, the ratio between the inner diameter and the length of the through hole is preferably in the range of 1/50 to 1/1. More preferably, it is in the range of 1/20 to 1/5. The inner diameter of the through hole should be determined in consideration of the outer diameter of the glass rod to be obtained, and can be set to 10 to 100 mm, for example. At that time, the length of the through hole is preferably in the range of 100 to 500 mm. Here, as shown in FIG. 3, the “length of the through hole” means a length along the central axis from the center of the surface including the casting port to the center of the surface including the drawing port.

  In the present invention, if necessary, the glass rod drawn from the through hole is subjected to annealing or the like after the annealing as shown in FIG. 1 in order to change the conveyance path of the rod-like glass drawn from the through hole before annealing. It may be bent in a direction that facilitates the process. FIG. 1 shows a mode in which annealing is performed after bending in the horizontal direction. In addition, before changing the conveyance path of the glass rod, in order to prevent breakage or distortion, the glass rod pulled out from the drawer port is heated again so that the surface temperature is equal to or higher than the glass transition point. And may be softened. However, excessive heating deteriorates the shape of the glass rod or alters the side surface of the glass rod. Therefore, when heating is performed, the heating temperature should be determined in consideration of this point. Heating can be performed, for example, by providing a heater in the vicinity of the driven roller 15 shown in FIG.

  In FIG. 1, a driven roller 15 and a driving roller 16 are shown. In the apparatus as shown in FIG. 1, the force for pulling out the glass rod can be obtained by rotation of the drive roller 15, and by passing the glass rod between the driven roller and between the drive rollers, the glass rod is moved in the desired direction. It can be bent (horizontal in FIG. 1). In order to stably pull out the glass rod, it is preferable that the positions of the driven roller 15 and the driving roller 16 are fixed. The number of driven rollers and drive rollers is not particularly limited as long as the glass rod can be pulled out and bent in a desired direction. The glass rod pulled out from the pull-out port is subjected to a subsequent process through a driven roller and a driving roller. Examples of the post-process include an annealing process, a process of cutting to a certain length, a packing process, and the like, and a homogeneous rod-shaped glass molded body can be obtained through post-processes such as annealing. The glass after the annealing step can be cut into a glass rod having an appropriate length, or can be cut into a glass block having a desired size for use as a glass material for press molding.

  FIG. 2 shows another example of the first aspect of the present invention, and is a schematic view from the side of a state in which a molten glass is cast and formed into a rod-shaped glass. As in FIG. 1, the portion of the mold 11 'is shown in a vertical cross section so that the inside can be seen. The viscosity of the molten glass to be cast is as described above.

  In the embodiment shown in FIG. 2, there is no driven roller and the driving roller 16 pulls out straight and transfers to a subsequent process including annealing without changing the transport path of the glass rod that has exited the drawer port. The other points are the same as the embodiment shown in FIG.

  In the present invention, as shown in FIG. 1 and FIG. 2, the liquid level monitoring device 17 is used to monitor the molten glass liquid level in the mold through-hole, and the speed at which the molten glass flows out from the outflow pipe 12. It is also possible to feed back to the rotation speed of the drive roller 16 so that the liquid level of the molten glass in the through-hole is kept constant while being kept constant. The liquid level monitoring device is not particularly limited as long as the liquid level can be monitored and fed back to the driving roller, and the liquid level can be monitored by, for example, a thermometer or a laser sensor.

  The material of the mold used in the present invention is preferably a heat-resistant metal such as carbon, casting or nickel. When temperature control is not performed, the temperature on the casting port side becomes higher than the temperature on the drawing port side during molding. Therefore, if the mold through hole is formed with a constant inner diameter at room temperature, the through hole is formed during molding due to thermal expansion. The inner diameter will not be constant. In the present invention, it is preferable to determine the processing shape of the through hole in consideration of thermal expansion so that the inner diameter of the through hole is increased from the casting port to the drawing port and the inner diameter of the through hole becomes constant at the time of molding. In the present invention, the step of producing a glass rod from molten glass is preferably performed in an inert atmosphere from the viewpoint of preventing deterioration of the mold.

  There is no restriction | limiting in particular in the shape of the glass rod shape | molded using the method of this invention, A cylinder, an elliptic cylinder, a prism etc. can be illustrated. In order to obtain a homogeneous glass rod having a desired cross-sectional shape, the mold should be designed so that the cross-sectional shape perpendicular to the central axis of the glass rod and the cross-sectional shape perpendicular to the central axis of the mold through hole coincide. Is preferred. In addition, the manufacturing method of the first aspect of the present invention is more suitable for forming a rod-shaped glass having a long / short ratio in the cross section, for example, a ratio of a long diameter to a short diameter (long diameter / short diameter) of 1 to 2. In the case of forming a glass rod having a major axis to minor axis ratio of 1 to 2 in the cross section, the angle θ formed by the central axis of the through hole and the horizontal plane is preferably in the range of 30 to 60 °.

Using the method of the present invention, a solid glass cylinder made of optical fiber cladding glass is formed, a hole corresponding to the cylinder axis is made into a hollow glass, and then an optical fiber core is placed in the hole. Glass fiber preforms can also be made by fitting glass cylinders made of glass. It is also possible to make a glass fiber preform by fitting a glass column for glass formed by the method of the present invention into a glass column for cladding with a hole in the center. The above two methods can be combined. Such a preform can be drawn to produce an optical fiber.
It is also possible to arrange a cylindrical shaft made of a heat-resistant material on the central axis of the mold through-hole, and pour molten glass into a hollow glass molded body having a hole on the central axis. The method of the present invention should be applied to obtain a solid columnar (non-hollow) glass because the flow of the molten glass poured in may disturb the flow of the molten glass.

As described above, the situation in which striae are likely to occur when the glass molded body is formed includes a case where a low-viscosity molten glass is poured to form glass and a case where plate glass is formed. According to the manufacturing method of the first aspect, a glass having no striae can be manufactured from a low-viscosity molten glass having a viscosity of ¹ dPa · S or more and less than 10 ² dPa · S.
Next, the second aspect of the present invention for forming a sheet glass will be described.

(Second embodiment)
The second aspect of the present invention is:
In a method for producing a glass molded body, in which molten glass is molded into a sheet glass while being poured into a through-hole of a mold having a through-hole,
In the through hole, two openings are connected linearly,
The mold is arranged so that the central axis of the through hole is inclined,
The molten glass is continuously poured from the opening on the high position side of the through hole, the plate glass is continuously drawn from the opening on the low position side of the through hole, and the molten glass is poured, It is a manufacturing method of the glass forming body characterized by performing while maintaining the molten glass liquid level in the opening part in a high position side at predetermined | prescribed height.

  According to the manufacturing method of the second aspect, since only the molten glass liquid surface in the mold is exposed to the outside air with the high temperature glass, striae caused by volatilization from the high temperature glass can be reduced. Further, since the flow direction of the molten glass in the mold is not suddenly bent, striae inside the glass can be reduced.

  The sheet glass has two main surfaces facing each other. In the manufacturing method of the second aspect, in the cross section perpendicular to the central axis of the through hole, the two molding surfaces for molding the main surface of the sheet glass are arranged symmetrically with respect to the central axis, It is preferable that the inclination angle of the central axis with respect to the horizontal direction is equal to the inclination angle of the molding surfaces with respect to the horizontal direction.

Hereinafter, the second embodiment of the present invention will be described with reference to FIG.
In the second aspect of the present invention, when the mold is arranged so that the central axis of the through hole is inclined, the mold through hole contacting the short side of the molten glass liquid surface when viewed from above vertically is used. The mold is such that the inner wall surface is perpendicular to the horizontal plane, that is, as shown in FIG. 4, the length of the short side a of the molten glass liquid surface is longer than the thickness t of the sheet glass. Is preferably inclined. By arranging the mold in this way, the ratio of the short side to the long side (short side / long side) when the molten glass liquid surface in the mold is viewed from above is determined by the inclination angle of the central axis with respect to the horizontal direction. It increases as it increases. That is, by inclining the mold through-hole central axis, the ratio of the above (short side / long side) of the molten glass liquid surface is larger than the ratio of the thickness to the width of the glass sheet to be formed (thickness / width). can do. According to the second aspect of the present invention, when producing a sheet glass having a rectangular cross-sectional shape with a ratio of width to thickness (width / thickness) of more than 2, the above-mentioned surface of the molten glass liquid surface By increasing the ratio of (short side / long side), the cast glass can be spread almost uniformly in both the short side direction and the long side direction, and the flow of glass in the mold cannot be greatly biased. Therefore, striae can be reduced.

The inclination angle of the central axis may be in the same range as in the first aspect. In particular, in the second aspect, the ratio (short side / long side) of the molten glass liquid surface is within the range. It is preferable to be close to 1. When the inclination angle of the central axis is θ, the thickness of the sheet glass is t, and the width is w, the short side a of the molten glass liquid surface can be expressed by t / sin θ, and the long side is w. Therefore, the ratio of the short side / long side is t / (w · sin θ). And when the said ratio is set to 1, it is when the inclination | tilt angle (theta) is sin < ^-1 > (t / w).

  The production method of the second aspect is suitable for forming a sheet glass having a thickness to width ratio (thickness / width) of 0.5 or less. A more preferable range of the ratio (thickness / width) is 0.05 to 0.5.

Moreover, it is preferable that the viscosity of the molten glass poured is ¹ dPa · s or more and less than 10 ² dPa · s. Also, in the second aspect, as in the first aspect, the position where the molten glass is poured is centered when the molten glass liquid surface in the mold is viewed from directly above. It is preferable from the viewpoint of preventing the striae by evenly spreading.
About another point, it can be made to be the same as that of said 1st aspect.

  In the first and second embodiments, the mold is preferably fixed by holding the upper part of the mold. The reason is that heat is taken away from the portion holding the mold and the mold contracts. As the mold shrinks, the size of the through hole also decreases. Even if the inner dimension (inner diameter in the case of rod-shaped glass) of the through hole is slightly reduced, the drawing of the molded glass is not hindered. However, if the inner dimension of the low position is decreased, the glass pulling is hindered. This is because there is a risk of being taken.

In this invention, the glass used as the raw material for obtaining a glass molded object is not specifically limited. According to the production method of the present invention, a glass with high homogeneity can be obtained without generating striae. Therefore, the production method of the present invention is a method for producing a glass molded body from optical glass that requires extremely high quality. In order to obtain, it can use suitably. Examples of such glass include SiO ₂ —TiO ₂ -containing glass, SiO ₂ —R ₂ O (R is at least one or a plurality of alkali metals of Li, Na, and K), B ₂ O ₃ —R ₂ O (R Is at least one or more alkali metals of Li, Na, K), P ₂ O ₅ —R ₂ O (R is at least one or more alkali metals of Li, Na, K), P ₂ O ₅ —TiO ₂ Examples thereof include optical glasses such as _2- containing glass, P ₂ O ₅ —Nb ₂ O ₅ -containing glass, B ₂ O ₃ —La ₂ O ₃ -containing glass, and fluorophosphate glass.

  The present invention also relates to a method for manufacturing a glass material for press molding, which includes a step of cutting the glass molded body obtained by the method for manufacturing a glass molded body of the present invention so as to cross its central axis.

  In the method for producing a glass material for press molding according to the present invention, the rod-shaped glass or plate-shaped glass obtained by the above-described method for producing a glass molded body according to the present invention is centered using, for example, a wire, a grindstone or the like. A glass block can be obtained by cutting across the axis. In consideration of the shape and dimensions of the desired glass material for press molding, it is preferable to determine the outer diameter of the glass rod to be molded and the width and thickness of the glass plate to be molded. The width | variety which cut | disconnects a glass stick | rod or a glass plate can be suitably set according to the thickness of the press molded product and optical element to be obtained. The obtained glass block can be heated and softened as it is and then press-molded to obtain a press-molded product, or a glass block that has been ground or polished can be heated and softened and then press-molded. Press-molded products can also be obtained. In this specification, a glass article that can be press-molded when heated and softened in this manner is referred to as a “press-molding glass material”. The press-molding glass material thus produced is heated and softened and then press-molded to obtain a press-molded product. Press molding can be performed by a known method. A molded product produced by press molding can be used as an optical element as it is, or the press molded product can be ground and polished to be finished into an optical element. An optical element such as a lens can also be made by subjecting a glass material for press molding to grinding and polishing without press molding. In this case, it is preferable to mold a glass rod having an outer diameter equal to the outer diameter of the optical element to be obtained or an outer diameter obtained by adding a machining allowance to the outer diameter. The width of the slice processing can be the thickness of the optical element or the thickness of the optical element plus a processing allowance. If the glass thus sliced is further ground and polished, optical elements such as lenses and prisms can be produced.

  When producing an axially symmetric optical element such as a lens by press molding, a cylindrical glass rod is preferably molded and cut perpendicularly to the central axis of the glass rod. In other cases, it is preferable to determine the shape of a glass material for press molding suitable for press molding from the shape of a desired optical element, and to mold a glass rod having such a shape that the material can be easily produced. The weight of the glass material for press molding obtained by cutting the glass rod can be made equal to the weight of the optical element to be obtained. Alternatively, it is possible to obtain a press-molding glass material having a weight of a desired press-molded product by performing machining after cutting.

  When manufacturing an optical element by precision press molding in which the optical functional surface of the optical element (the surface for refracting, reflecting, or diffracting the light beam to be controlled) is formed by press molding, It is desirable to finish the surface of the glass material for press molding smoothly. Further, when press molding is performed in an oxidizing atmosphere, the release film (for example, made of carbon) may be deteriorated. Therefore, the press molding is preferably performed in a non-oxidizing atmosphere.

When precision press molding is performed, the obtained press-molded product is cooled slowly, and then, as it is, various lenses such as aspherical lenses, spherical lenses, microlenses, lens arrays, prisms, polygon mirrors, diffraction gratings, filters, etc. It can be used as various optical elements. If necessary, the surface around the optical functional surface may be machined to finish the optical element.
Further, as another aspect, the glass material for press molding is heated and softened in the air, for example, and then press-molded to form a press-molded product, and the press-molded product is ground and polished to obtain various lenses, prisms, etc. An optical element can also be produced.

Hereinafter, the present invention will be described in more detail with reference to examples.

(Example 1)
Thoroughly clarified and homogenized molten glass (glass viscosity of 10 dPa · s) is continuously flowed from the outflow pipe at a constant outflow rate (106 ml / min), and is provided in a carbon mold placed at the position shown in FIG. Poured into the center of the through hole. The inner diameter of the mold through hole was φ30 mm, and the angle θ formed by the central axis of the through hole and the horizontal plane was 45 °. The length of the mold through hole was 250 mm, and a band heater (not shown) was wound around the mold and heated so that good molding was possible. The rotational speed of the driving roller was set so that the glass rod drawing speed was 15 cm / min, and a glass rod (round bar) with a diameter of 30 mm was drawn. The glass rod was bent in the horizontal direction by a driven roller and a driving roller, and then annealed to remove distortion.
Thus, to produce a glass rod made of an optical glass comprising SiO _2, TiO ₂ and alkali metal oxides. The obtained solid columnar glass rod was homogeneous and transparent, and no defects such as striae were observed.

(Example 2)
A mold as shown in FIG. 2 was placed so that θ was 10 °, and a glass rod (round bar) having a diameter of 20 mm was formed. At this time, the outflow speed of the molten glass (glass viscosity 5 Pa · s) was 47 ml / min, and the drawing speed of the glass rod was 15 cm / min. In this example, the drawn solid columnar glass rod was annealed as it was without bending.
Thus, to produce a glass rod made of an optical glass comprising SiO _2, TiO ₂ and alkali metal oxides. The obtained glass rod was homogeneous and transparent, and no defects such as striae were observed.
In Examples 1 and ₂ , even if an optical glass other than the optical glass containing SiO ₂ , TiO ₂ and an alkali metal oxide is used, good molding is possible.

(Example 3)
The glass rods molded in Examples 1 and 2 were cut in a direction perpendicular to the central axis to form a cylindrical block having a thickness of 10 mm. Further, the cylindrical block was ground or polished to produce an axisymmetric shaped glass material for press molding. No defects such as striae were observed in the press-molding glass material thus produced.
Further, the obtained cylindrical block can be ground and polished without press molding to produce an optical element such as a lens. In the optical element thus obtained, no defects such as striae were observed.

Example 4
The glass material for press molding having a smooth surface produced in Example 3 is heated, softened, precision press-molded using a press mold in a mixed gas atmosphere in which hydrogen is mixed with nitrogen, and annealed to obtain an aspheric lens. Got. The obtained lens was good without defects such as striae.

(Example 5)
The glass material for press molding produced in Example 3 was heated and softened, press-molded using a press mold in the atmosphere, and annealed to obtain a spherical lens. The lens produced in Example 5 was good without defects such as striae.

(Example 6)
The mold used in Example 1 was replaced with a mold whose vertical cross section with respect to the central axis of the through-hole was rectangular (vertical 20 mm, horizontal 200 mm), and the angle θ formed by the through-hole central axis and the horizontal plane was set to 30 °. The mold was placed so that the opening on the side was directly below the outflow pipe. At this time, the long side of the vertical cross section of the through hole is made horizontal. Then, molten glass (glass viscosity of 10 dPa · s) is continuously flowed from the outflow pipe to the opening at a constant outflow rate (150 ml / min), and is formed into a sheet glass having a thickness of 20 mm and a width of 200 mm, and the mold lower position side It was pulled out from the opening. The plate glass was bent in the horizontal direction by the driven roller and the driving roller in the same manner as in Example 1, and then annealed to remove the distortion. The glass used was the same as in Example 1.
In this way, a glass plate made of optical glass that was homogeneous and transparent and free from defects such as striae could be produced.

(Example 7)
The mold used in Example 2 was changed to one having a vertical cross-sectional shape with respect to the central axis of the through hole being rectangular (vertical 10 mm, horizontal 100 mm), and the angle θ formed between the central axis of the through hole and the horizontal plane was set to 45 °. The mold was placed so that the opening on the side was directly below the outflow pipe. At this time, the long side of the vertical cross section of the through hole is made horizontal. Then, the molten glass is continuously flowed from the outflow pipe to the opening at a constant outflow speed (50 cc / min), formed into a sheet glass having a thickness of 10 mm and a width of 100 mm, and drawn from the opening on the lower mold side. In the same manner as in Example 2, the strain was removed by annealing without bending. The glass used was the same as in Example 2, and the viscosity of the molten glass when poured into the mold was 5 dPa · s.
In this way, a glass plate made of optical glass that was homogeneous and transparent and free from defects such as striae could be produced.

(Example 8)
The plate-like glass molded in Examples 6 and 7 is cut vertically and horizontally perpendicular to the main surface of the glass plate, glass pieces called cut pieces are made, barrel-polished, chamfered and weight adjusted, and pressed. A glass material for molding was used. And the said raw material was heated and softened in air | atmosphere, and it press-molded and produced the lens blank. Next, the lens blank surface was ground and polished to finish the lens.
Further, the cut piece was polished to obtain a glass material for press molding having a smooth surface. And the said glass raw material was precision press-molded by the method similar to Example 4, and the aspherical lens was obtained.
All the lenses in this example were good without defects such as striae.

  According to the present invention, a glass molded body having no striae or very few can be produced with high productivity. The manufacturing method of the present invention is to manufacture and store a glass molded body made of various optical glasses, and make a glass material for press molding by machining such as cutting into a predetermined dimension according to demand, or the glass By pressing the material and manufacturing the optical element, it is possible to respond flexibly and quickly to demand.

It is one aspect | mode of the manufacturing method of the glass molded object of this invention. It is one aspect | mode of the manufacturing method of the glass molded object of this invention. It is explanatory drawing of the length of a casting_mold | template. It is explanatory drawing of the 2nd aspect of this invention.

Claims (8)

In a method for producing a glass molded body in which molten glass is molded into a solid rod-like glass while being poured into a through-hole of a mold having a through-hole,
In the through hole, two openings are connected linearly,
The mold is arranged so that the central axis of the through hole is inclined,
A molten glass having a viscosity of ¹ dPa · S or more and less than 10 ² dPa · S is continuously poured from the opening on the high position side of the through hole, and the rod-shaped glass is continuously poured from the opening on the low position side of the through hole. A method for producing a glass molded body, characterized in that the molten glass is drawn out and the molten glass is poured while maintaining a molten glass liquid level at an opening on the high position side at a predetermined height. In a method for producing a glass molded body, in which molten glass is molded into a sheet glass while being poured into a through-hole of a mold having a through-hole,
In the through hole, two openings are connected linearly,
The mold is arranged so that the central axis of the through hole is inclined,
The molten glass is continuously poured from the opening on the high position side of the through hole, the plate glass is continuously drawn from the opening on the low position side of the through hole, and the molten glass is poured, A method for producing a glass molded body, wherein the molten glass liquid level in the opening on the high position side is maintained at a predetermined height. The manufacturing method of the glass forming body of Claim 1 or 2 which controls the temperature of a casting_mold | template so that the surface temperature of the glass withdraw | derived from a through-hole may become below a glass yield point. When changing the conveyance path | route of the glass pulled out from the through-hole before annealing, glass is heated so that the surface temperature of glass may become more than a glass yield point before a conveyance path | route change. The manufacturing method of the glass molded object as described in a term. The manufacturing method of the glass raw material for press molding including the process of cut | disconnecting the glass molded object manufactured by the method of any one of Claims 1-4 so that the central axis may be crossed. The method for producing a glass material for press molding according to claim 5, further comprising a step of machining the cut glass to produce a glass material for press molding. A method for producing an optical element, comprising heating and softening a glass material for press molding produced by the method according to claim 5 or 6 and then press-molding to obtain a press-molded product. The method for manufacturing an optical element according to claim 7, further comprising a step of grinding and / or polishing the press-formed product.